A 20-gallon aquarium tank alone costs $25 to $75, depending on shape and material

The glass or acrylic tank itself—just the container—runs between $25 and $75 new. A standard rectangular 20-gallon tank (24 inches long, 12 inches wide, 12 inches tall) typically costs $30 to $50 at most pet supply stores. A 20-gallon tall tank (a different shape, 24 inches long, 12 inches wide, 24 inches tall) or a 20-gallon long tank (30 inches long, 12 inches wide, 12 inches tall) may cost slightly more. Acrylic tanks cost more than glass but weigh less and are harder to scratch during setup.

The total cost to set up a working 20-gallon aquarium—tank, filter, heater, substrate, decorations, and lighting—ranges from $150 to $400 for a basic freshwater setup. A saltwater or reef setup costs considerably more because the equipment and maintenance materials are specialized. This guide covers what drives those costs and where the money actually goes.

Key Takeaways

  • A bare 20-gallon tank costs $25 to $75; a complete working setup costs $150 to $400 for freshwater fish.
  • A filter, heater, and lighting are required equipment that together cost $80 to $200, depending on quality and brand.
  • Substrate, plants, decorations, and a stand add $40 to $100 to your setup cost.
  • Saltwater or reef tanks require specialized equipment and cost significantly more than freshwater setups.
  • Ongoing costs for food, water treatments, and filter media run $10 to $30 per month.

What you need beyond the tank itself

A 20-gallon aquarium cannot hold fish safely with only a tank. You need a filter to remove waste and keep water clean, a heater to maintain temperature (unless you keep cold-water fish), lighting to see the fish and support plant growth, and substrate (gravel or sand) for the bottom. Most beginners also buy a stand to hold the tank safely and decorations or plants to give fish places to hide.

A filter for a 20-gallon tank costs $20 to $80 depending on type. A hang-on-back filter (the most common for beginners) runs $20 to $50. An internal canister filter costs $40 to $80. A heater costs $15 to $40. Basic LED lighting built into a hood or strip costs $20 to $60. Substrate (gravel or sand) for a 20-gallon tank costs $10 to $25. A stand costs $40 to $100 or more, depending on material and whether you build one yourself.

Tank shape and material affect price

A standard rectangular 20-gallon tank is the cheapest option because it is the most common shape manufacturers produce. A 20-gallon tall or 20-gallon long costs about the same or slightly more because fewer people buy them, so fewer are made. Acrylic tanks cost 20 to 40 percent more than glass but are lighter and less likely to crack if bumped during setup. Rimless glass tanks (with no frame around the top edge) cost more than framed tanks because they require thicker glass and more precision in manufacturing.

The shape you choose affects what equipment you need. A tall tank is narrower, so you may need a different filter or heater size. A long tank is shallower, which some fish prefer. Check the dimensions before you buy so the filter and heater you choose will fit and work properly in that specific shape.

Where the rest of the setup cost goes

Decorations, plants, and hiding spots add $20 to $60 to your setup. Live plants cost more than plastic ones but improve water quality and look more natural. Driftwood, rocks, and caves run $10 to $40 depending on size and type. A basic plastic plant costs $2 to $8; a live stem plant costs $3 to $10.

Water treatments and test kits cost $15 to $40 upfront. You need a water conditioner to remove chlorine from tap water before adding it to the tank, and a test kit to measure ammonia, nitrite, and nitrate levels while the tank cycles (the process of establishing beneficial bacteria). Some people buy a gravel vacuum for water changes, which costs $15 to $30. Others use a straightforward siphon hose, which costs $5 to $10.

Saltwater and reef setups cost significantly more

A saltwater 20-gallon tank costs $300 to $600 for the basic setup because the equipment is specialized. You need a protein skimmer (which removes waste from the water), a powerhead (a strong water pump), and specialized salt mix. Live rock and live sand, which are essential for saltwater tanks, cost $50 to $150 alone. A reef setup (which includes corals) costs $400 to $800 or more because corals require high-quality lighting, which can cost $100 to $300 by itself.

Saltwater tanks also require more frequent testing and more expensive water treatments. If you are new to aquariums, a freshwater setup is a better starting point because it is cheaper and more forgiving of beginner mistakes.

Ongoing monthly costs after setup

Once your tank is running, expect to spend $10 to $30 per month on maintenance. Fish food costs $5 to $10 per month depending on the type and number of fish. Filter media (cartridges or sponges you replace every 4 to 8 weeks) costs $3 to $8 per replacement. Water conditioner and test kits cost $2 to $5 per month if you test regularly. If you keep live plants, fertilizer costs $2 to $5 per month.

Saltwater tanks cost $20 to $50 per month because salt mix, specialized additives, and live food are more expensive. Budget for occasional equipment repairs or replacements—a heater may fail after a year or two, or a filter may need a new motor.

How to save money on your first setup

Buy a kit instead of buying each piece separately. A 20-gallon aquarium kit (tank, filter, heater, and lighting together) costs $80 to $150, which is cheaper than buying each item individually. Kits are usually made by the same manufacturer, so the pieces fit together properly.

Buy a used tank if you can inspect it first. A used 20-gallon tank in good condition costs $15 to $40. Check for cracks, chips, or cloudy spots in the glass. Avoid tanks with visible damage or ones that have been sitting empty for years, because old silicone seals may leak. Used filters and heaters are riskier because you cannot see inside them, so buy those new unless you know the person selling them.

Start with hardy fish that tolerate beginner mistakes—goldfish, tetras, and corydoras catfish are forgiving. Avoid expensive fish until you have experience. Expensive fish often require specific water conditions and die easily if those conditions are not perfect.

Frequently Asked Questions

Is a 20-gallon tank big enough for fish?

Yes, a 20-gallon tank is large enough for many common freshwater fish. Small fish like tetras, guppies, and corydoras catfish do well in 20 gallons. Larger fish like goldfish or plecos need bigger tanks. Check the adult size of the fish you want before you buy it, because a fish that is small at the pet store may grow too large for your tank.

Can I use a 20-gallon tank without a heater?

Only if you keep cold-water fish like goldfish or certain tetras. Most tropical fish need water between 75 and 80 degrees Fahrenheit, which requires a heater unless your room stays that warm year-round. A heater costs $15 to $40 and is worth the investment because temperature swings stress fish and cause disease.

How long does it take to set up a 20-gallon tank?

Assembly takes 1 to 2 hours. Filling the tank, adding substrate, and arranging decorations takes another 1 to 2 hours. The tank then needs to cycle for 4 to 6 weeks before you add fish, during which beneficial bacteria establish themselves in the filter and substrate. You can add hardy fish after 2 weeks if you test the water daily and do partial water changes.

What is the difference between a 20-gallon tall and a 20-gallon long?

A 20-gallon tall is 24 inches long, 12 inches wide, and 24 inches tall. A 20-gallon long is 30 inches long, 12 inches wide, and 12 inches tall. Both hold 20 gallons of water. A long tank gives fish more swimming space side to side; a tall tank takes up less floor space. For most fish, a long tank is better because fish swim horizontally more than vertically.

Do I need to buy a stand for my 20-gallon tank?

A stand is not required, but it is strongly recommended. A 20-gallon tank filled with water weighs about 170 pounds. A stand designed for that weight distributes the load safely and keeps the tank at a comfortable viewing height. Placing a tank on a bookshelf or dresser risks collapse and serious injury. A stand costs $40 to $100, which is worth the safety and convenience.